In a process of manufacturing electronic devices such as semiconductor devices or liquid display devices, treatment such as film formation on an object or etching for the object is carried out. A plasma processing apparatus has been widely used for such treatment for the object. For example, a parallel plate type plasma processing apparatus has been used.
The parallel plate type plasma processing apparatus includes a processing chamber, a mounting table and a shower head. The mounting table includes a lower electrode and is provided in the processing chamber. The shower head is provided above the mounting table and supplies a processing gas toward the object mounted on the mounting table. Further, the shower head serves as an upper electrode. In the parallel plate type plasma processing apparatus, the processing gas is supplied from the shower head into the processing chamber, and a high frequency electric field is generated between the upper electrode and the lower electrode. Accordingly, a plasma of the processing gas is generated and the object is processed by active species of atoms and/or molecules in the processing gas.
In this plasma processing apparatus, it is required to reduce non-uniformity of the treatment for the object in the surface of the object (hereinafter, referred to as “in-plane non-uniformity”). The following Patent Document 1 discloses a plasma processing apparatus capable of controlling a flow rate and/or a type of the processing gas supplied toward a plurality of regions in the surface of the object in order to reduce the in-plane non-uniformity.
Specifically, in the plasma processing apparatus disclosed in Japanese Patent Application Publication No. 2009-117477, the shower head has a facing plate. The facing plate has a plurality of coaxial regions, and a plurality of gas injection holes is formed in each of the regions. Further, a plurality of gas diffusion spaces is coaxially formed immediately above the facing plate. In other words, a first gas diffusion space is formed immediately above a first region at the center of the facing plate. A second gas diffusion space is formed immediately above a second region of the facing plate extending in an annular shape at the outer side of the first region. A third gas diffusion space is formed immediately above a third region of the facing plate which extends in an annular shape at the outer side of the second region. The first gas diffusion space is connected to a plurality of gas injection holes formed in the first region. The second gas diffusion space is connected to a plurality of gas injection holes formed in the second region. The third gas diffusion space is connected to a plurality of gas injection holes formed in the third region.
Further, the plasma processing apparatus of Japanese Patent Application Publication No. 2009-117477 has a plurality of gas branch lines, i.e., a plurality of gas inlet lines, and a gas from a source gas is supplied into a plurality of gas diffusion spaces through the gas inlet lines. Specifically, a first gas inlet line connected to a first gas diffusion space extends along the central axes of the first to the third gas diffusion spaces. Meanwhile, a second and a third gas inlet line respectively connected to the second and the third gas diffusion space extend while being spaced apart from the central axes. Accordingly, the second and the third gas inlet line are connected to the second and the third gas diffusion space while being spaced apart from the central axes of the second and the third gas diffusion space, respectively.
In the plasma processing apparatus of Japanese Patent Application Publication No. 2009-117477, flow rates of gases injected from the gas injection holes formed in the second region may be not uniform. Further, flow rates of gases injected from the gas injection holes formed in the third region may be not uniform. In other words, the gas injection holes directly connected to the same gas diffusion space have different injection amounts depending on whether or not they are formed near the connection position of the gas inlet line. As a result, in-plane non-uniformity may occur in the processing of the object.